A latent heat storage material using absorption of heat and generation of heat occurring during a phase change of liquid-solid is known to be in a state of supercooling that maintains a molten state even if a temperature decreases to the melting point or less after the latent heat storage material is in the molten state once. Since it is possible to provide heat release according to the phase change by artificially releasing the state of supercooling, the use of the latent heat storage material grows as a material that allows switching of heat storage-heat release. In recent years, developments of a technique of microparticulating this latent heat storage material and thereafter encapsulating it to improve the speeds of heat release and heat storage, and a technique of suppressing coalescence when being molten to facilitate transporting and treating are underway.
Examples of a known method for producing a capsule including these phase-change materials include a technique of producing a microcapsule including the paraffins by the step of heating paraffins to a melting point or higher thereof, cooling a heat storage material emulsion obtained by performing emulsification and dispersion in an aqueous solution in a pressurization state, thereafter performing a reheating, and performing microencapsulation using a melamine-formaldehyde resin or a urea-formaldehyde resin as a coat according to an In-situ polymerizing method (for example, see Patent Literature 1 below), a technique of producing a heat storage microcapsule by using xylitol that stores heat or releases heat according to a phase change as a core substance, and covering the core substance with an aramid resin (for example, see Patent Literature 2 below), and a technique of producing a heat storage microcapsule by microparticulating an aqueous solution of a core substance using a dispersion film, and causing a reaction with isocyanate (for example, see Patent Literature 3 below).